Application of high &amp;amp; low brightness LEDs to human tissue to capture photoplethysmogram at a finger tip

Shriram, Revati; Sundhararajan, M.; Daimiwal, Nivedita

doi:10.1109/i2ct.2014.7092340

Cited by 3 publications

(4 citation statements)

References 2 publications

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“…The results have also shown how the detected amplitude is viewing-angle dependent. This is an expected result that also matches what Shriram et al found, 16 since the bigger the angle, the less the light is concentrated in a given skin region, where fewer photons will arrive at a photodetector placed on the surface of that region. Nevertheless, the results stress the need to include the LED viewing angle value as a key parameter in the system characterization.…”

Section: Discussionsupporting

confidence: 88%

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Evaluation of the impact of LED viewing angle and optical window choice on photoplethysmography signal quality

Sole Morillo,

Lambert Cause,

Rizk

et al. 2024

Optical Fibers and Sensors for Medical Diagnostics, Treatment, and Environmental Applications XXIV

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Photoplethysmography (PPG) is a non-invasive optical technique used to extract physiological information by means of light interaction with the skin. PPG is widely used in pulse oximeters, and the evolution of wearable technologies is further enlarging its applications. A great variety of influencing factors impact the PPG waveform, making the correct feature extraction difficult and, therefore, limiting the accuracy of many PPG applications. The device hardware and software are among these influencing factors. This study evaluates the impact on the PPG signal quality of the LED viewing angle (luminous aperture) and the protective glass material, thickness, and anti-reflective coating, both important building blocks of a PPG sensor. Results suggest that the larger the viewing angle, the smaller the detected signal amplitude. The protective glass properties on the contrary does not seem to impact the detected signal amplitudes.

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Section: Discussionsupporting

confidence: 88%

“…Another study evaluated the impact of the LED viewing angle and diameter on the PPG amplitude. 16 The LEDs were divided into clear or diffused, and no numeric half angle was given. The study shows a bigger signal amplitude when clear LEDs are used.…”

Section: Monochromaticmentioning

confidence: 99%

Evaluation of the impact of LED viewing angle and optical window choice on photoplethysmography signal quality

Sole Morillo,

Lambert Cause,

Rizk

et al. 2024

Optical Fibers and Sensors for Medical Diagnostics, Treatment, and Environmental Applications XXIV

View full text Add to dashboard Cite

show abstract

“…With the increasing traditional energy resource crisis and environmental pollution arising from electrical production, the appealing light-emitting diodes (LEDs) have become a competitive candidate for next-generation solid-state lighting devices because of their high energy efficiency, small size, high color rendering index, reliable lifetime, and wide spectral line width from deep ultraviolet to yellow. − Currently, LEDs are considered extensively as industry-focused optoelectronic devices for illumination in high-value applications, such as smartphones, traffic lights, automotive headlights, full-color displays, home lighting, backlighting source in liquid-crystal displays (LCDs), LED displays, and other medical and commercial devices. − In addition, the 2014 Nobel Prize in Physics was given to Shuji Nakamura’s and Akasaki’s groups for the invention of efficient blue LEDs, which has enabled bright and energy-saving white light sources . This invention recognizes the significance of environment-friendly LEDs and attained considerable attention in further optimization.…”

Section: Introductionmentioning

confidence: 99%

Insights into the Silver Reflection Layer of a Vertical LED for Light Emission Optimization

Khan¹,

Chen²,

Qu³

et al. 2017

ACS Appl. Mater. Interfaces

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In this work, Ag as a highly reflective mirror layer of gallium nitride (GaN)-based blue vertical light-emitting diodes (VLEDs) has been systematically investigated by correlating scanning electron microscopy/energy dispersive X-ray spectroscopy/transmission Kikuchi diffraction/electron backscatter diffraction, aberration-corrected scanning transmission electron microscopy, and atomic force microscopy techniques. In the context of high-efficiency lighting, three critical aspects have been scrutinized on the nanoscale: (1) chemical diffusion, (2) grain morphology, and (3) surface topography of the Ag layer. We found that nanoscale inhomogeneous distribution of In in InGaN/GaN quantum wells (QWs), interfacial diffusion (In/Ga out-diffusion into the Ag layer and diffusion of Ag into p-GaN and QWs), and Ag agglomeration deteriorate the light reflectivity, which account for the decreased luminous efficiency in VLEDs. Meanwhile, the surface morphology and topographical analyses revealed the nanomorphology of the Ag layer, where a nanograin size of ∼300 nm with special nanotwinned boundaries and an extremely smooth surface of ∼3-4 nm are strongly desired for better reflectivity. Further, on the basis of these microscopy results, suggestions on light extraction optimization are given to improve the performance of GaN-based blue VLEDs. Our findings enable fresh and deep understanding of performance-microstructure correlation of LEDs on the nanoscale, providing guidance to the design and manufacture of high-performance LED devices.

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“…Because of features like simple in construction, compact, easy to use and inexpensive, these photon (sensing element) based optical sensors are becoming important. Optical sensing such as photoplethysmography is capable of measuring blood volumetric changes in the subcutaneous vessels [1]. The transmission type measurement has limitations based on measurement site.…”

Section: Introductionmentioning

confidence: 99%

Comparison of Acceleration Plethysmogram Acquired Using Optical Signal and Pressure Signal

Shriram¹,

Martin²,

Sundhararajan³

et al. 2017

IJSIP

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Application of high & low brightness LEDs to human tissue to capture photoplethysmogram at a finger tip

Cited by 3 publications

References 2 publications

Evaluation of the impact of LED viewing angle and optical window choice on photoplethysmography signal quality

Evaluation of the impact of LED viewing angle and optical window choice on photoplethysmography signal quality

Insights into the Silver Reflection Layer of a Vertical LED for Light Emission Optimization

Comparison of Acceleration Plethysmogram Acquired Using Optical Signal and Pressure Signal

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